The timeline on the right-hand side of the capsule editor offers easy access to the commit history and the ability to commit any changes you make:

NOTE: If you've never used Git before, you don't need to worry about version control. Code Ocean endeavors to provide version control for those who wish but not to disrupt existing functionality. If something is confusing, please let us know via live chat or an email to support@codeocean.com, and we will be happy to help.